Learning Forum

[Hanin Ayash]

I am using "import STL" to import a structure that is uniform along z but non uniform in the transverse direction. When I use FDTD, the simulation stops before it reaches the autoshut off threshold. While in RCWA, the index preview shows that the boundaries of the structures have an intermediate refractive index between the refractive index of the structure itself and the background. Simulations in RCWA and FDTD yield different results.

[Amrita Pati]

Hi Hanin,

If the FDTD simulation ends before reaching the auto shutoff level then you have to increase the simulation time in the General Tab of FDTD. I would recommend you to increase it by 10 times to be on the same side. After running the simualtion, if you click on the FDTD object, on the Results View tab, you should see a field called “status”, if the simulation has reached the auto shutoff at the end, the status must be 2.

For the intermediate indices that you see in RCWA, would you be able to share some screenshots and also more details on what you expect the indices in the regions to be? You may also include the coordinates of the interface positions. It might be due to the coarser RCWA mesh, but screenshots would definitely help. Thank you!

Regards,
Amrita

 

 

[Hanin Ayash]

I attempted to import the structure with a higher resolution and smoother corners. Despite these changes, the index profile shown here remained largely unchanged. Could retaining the boundaries in this manner lead to inaccurate results?

[Amrita Pati]

Hi Hanin,

Please try using more number of k-vectors in the transverse direction and also increase the number of interfaces along the propagation direction to see if the resolution of the index results is improved. I would ask you to perform convergence testing with respect to these two input parameters to confirm the accuracy of your results. We have also seen some inconsistent results from the index monitor recently (which I am not sure is of relevance here), for which we have contacted the R&D team. We will let you know as soon as we have more information.

Regards,
Amrita